Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction:
Dry friction is a force that opposes the relative lateral motion of two solid surfaces in contact. Dry friction is subdivided into static friction ("stiction") between non-moving surfaces, and kinetic friction between moving surfaces. With the exception of atomic or molecular friction, dry friction generally arises from the interaction of surface features, known as asperities (see Figure 1).
Fluid friction describes the friction between layers of a viscous fluid that are moving relative to each other.Lubricated friction is a case of fluid friction where a lubricant fluid separates two solid surfaces.Skin friction is a component of drag, the force resisting the motion of a fluid across the surface of a body.
Internal friction is the force resisting motion between the elements making up a solid material while it undergoes deformation.When surfaces in contact move relative to each other, the friction between the two surfaces converts kinetic energy into thermal energy (that is, it converts work to heat). This property can have dramatic consequences, as illustrated by the use of friction created by rubbing pieces of wood together to start a fire. Kinetic energy is converted to thermal energy whenever motion with friction occurs, for example when a viscous fluid is stirred. Another important consequence of many types of friction can be wear, which may lead to performance degradation or damage to components. Friction is a component of the science of tribology.
Friction is desirable and important in supplying traction to facilitate motion on land. Most land vehicles rely on friction for acceleration, deceleration and changing direction. Sudden reductions in traction can cause loss of control and accidents.
Friction is not itself a fundamental force. Dry friction arises from a combination of inter-surface adhesion, surface roughness, surface deformation, and surface contamination. The complexity of these interactions makes the calculation of friction from first principles impractical and necessitates the use of empirical methods for analysis and the development of theory.
Friction is a non-conservative force – work done against friction is path dependent. In the presence of friction, some kinetic energy is always transformed to thermal energy, so mechanical energy is not conserved.
Homework Statement
A 1450-kg car is towing a trailer of mass 454-kg. The force of air resistance on both vehicles is 7471N[backward]. If the acceleration of both vehicles is 0.225m/s^2[forward], what is the force of static friction on the wheels from the ground?
Homework Equations
Fnet = ma...
1. Homework Statement
i did part a,b,c but i am confused about part d.. i have a test tomorrow and will reattempt this when i wake up but i really need a hint here..so when the worker pulls upward he is decreasing the magnitude of -mg right? so if Fn and mg initially cancel each other out...
1. Homework Statement
in picture
Homework EquationsThe Attempt at a Solution
in picture, not sure if i am even doing this properly but i think i am? i am going to continue trying part b but please if you can let me know if i am doing this proper let me know...Thank you
1. Homework Statement
I have already solved this one weeks ago, and i have a test Tuesday so i was reviewing these problems.
I understand everything when solving with 60N as the force.. but then when i changed the force to 20N,
i had to use the coefficient of kinetic friction to get the correct...
Hi ,
The Static Friction force of an object on a ramp(inclined plane) making an angle with the horizontal is greater than the weight component down the ramp. My textbook says that this means that the object on the ramp is stationary as the frictional force is greater than the weight component...
Homework Statement
A child of an Eskimo decided to slide down an igloo. The igloo looks like a hemisphere with radius R. When will the child fall off the slide?
Homework Equations
See belowThe Attempt at a Solution
There are only two forces acting on the child - the force of gravity and the...
Homework Statement
A uniform chain of mass 'm' and length 'l' rests on a rough incline (inclination is angle 'Q') with its part hanging vertically. The chain (inclined) starts moving up the incline (and the vertical part moving down) provided the hanging (vertical) part equals to 'n' times...
Homework Statement
A 5.0kg block of wood sits on a table with a string running over a pulley suspending a mass. The largest mass that can be suspended without moving the block of wood is 0.75kg.
a) Calculate the coefficient of friction in this case.
b) What type of coefficient of friction has...
Homework Statement
Image below is a sketch of the situation. A pallet is vertically moved towards the conveyor. The purpose is that this stack of pallets (about 15 pallets) gets guided by 2 plate structures so that the stack is ligned out.
Homework Equations
I'm wondering now what the optimal...
Homework Statement
Homework EquationsThe Attempt at a Solution
If the two blocks were to move together when the external force of magnitude mg is applied , the acceleration would be mg/3m = g/3 . This acceleration would have to be provided by friction . Value of friction should be mg/3 . But...
Homework Statement
This is taken from a problem with its solution. But there's one thing I didn't understand with the solution:
A closed conductor loop is located perpendicular to the field lines in a homogeneous magnetic field B. The conductor slice CD is first in rest. Then we pull a...
This question is on our worksheet for this week. Part A and B-i I'm fine with.
Part B-ii I'm confused by. I've asked my physics lecturer and he implied there is a way of finding fs,max using part B-i. My class tutor was a bit confused by the wording of the question and tried to break part of...
Homework Statement
At a construction site, a small crane is raising two boxes of nails on a plank to the roof. One box has already been opened and is half full, while the other box is new. The boxes, including the nails, weigh 10 kg and 20 kg, respectively, and are both the same size.
c) If...
I am a bit confused.
We have an inclined plane.
So I know that Ffmax=μ*N and μ is the coefficient of friction calculated as tgθ (θ is the angle at which the body is on the verge of sliding) and also Ff<=Ffmax
And we know that the force that makes the body slide is mgsinθ.
So as the angle...
I have my students doing a lab where they have to do and explain the tablecloth trick using Newton’s Laws. The problem I am having is that the one question asks why the quick removal of the tablecloth matters. I know friction is not affected by speed and yet this is the only force acting on the...
Hi, I’m looking for some advice on materials. In the picture A, B and C are stainless steel. Pressure is applied at B rotating D in the socket and raising A. D needs to be as strong as possible to resist the load but I’m concerned about D rubbing against C as there is no lubrication. I can't...
Homework Statement
A 24 kg object is placed at the top of an incline with height 500m and length 375m. The coefficient of kinetic friction is 0.600
1) Find the acceleration of the object.
2) Find the speed by the time it has reached the bottom of the inclined plane.
Homework Equations
F_g =...
Hi there,
I am new here so please don't be too hard on me yet and move this post if i placed it in the wrong forum.
I am developing a little experiment game and i want the train to drive using real physics, but I am really bad at physics.
So my question is is how do I calculate the friction of...
Hi guys,
Yesterday I sat down, and just for fun, decided to calculate the coefficient of kinetic friction for the all electric Ford Focus. I keep getting the wrong answer, and it is driving me crazy. Here are the facts.
Battery: 23 kWh.
Curb weight: 1,651 kg.
Maximum travel distance before a...
Homework Statement
A phonograph record is whiring around at 103 rpm. Two balls of mass 1 kg are sitting on the disk and are at rest with respect to disk. The first ball (1) sits at a radius 5 away from center. The second ball (2) sits at a radius of 10 away from center. What is the ratio of...
Homework Statement
I don't remember exactly what the question was because it was on a quiz today. It said something along the lines of "a ladybug is on a turntable and begins to slip at .5 m/s. Find the coefficient of friction.
Homework Equations
Fc = (mv^2)/r
a = v^2/r
Ff = uFn
I think...
Homework Statement
Efficient and safe transportation depends on friction being either minimized or maximized as necessary.
a) One example in which friction is maximized to aid in transportation
a) One example in which friction is minimized to aid in transportation
For each situation, explain...
I've just been thinking, and I don't know why I couldn't figure this out on my own, but I got this question bugging me.
I was moving a sofa the other day. The sofa was against a wall. I started thinking why it was harder to push the sofa parallel to the wall when it was touching the wall rather...
If friction is independent of area of contact, how do less inflated tires of a bicycle experience more resistance towards motion than the well inflated tires?
Homework Statement
What is the maximum acceleration the train can achieve?
Engine effect=6500kW
μ(Friction Coefficient (between rails and wheels))=0.45
g=9.82N/kg
m(Train weight)=120,000kg
α=0
Homework Equations
Fμ=Fn*μ
Fn=cos(α)*m*g
a=F/m
The Attempt at a Solution
We've used the equations...
Homework Statement
When a disk rolls in a surface whitout slip, the velocity of the disk's edge (where it contacts the surface) is zero with respect the surface and the friction force is less than the maximum allowable of Us.N, where Us is the coefficient of static friction and N is the normal...
Homework Statement
I have no idea what torque of a friction in a bearing is. I'm looking for good explanation.
Homework EquationsThe Attempt at a Solution
I understand what torque/friction/bearing is. But I have no idea how they come together when looking at the actual mechanical problem. Help!
Homework Statement
I have a sphere, it's imperfectly spherical, I put it on an incline and apparently it needs a minimum friction to start rolling or moving. Homework Equations
I = 2/5 MR^2
torque = I*alpha = R x F
The Attempt at a Solution [/B]
before anything, I don't get why there's a...
Homework Statement
A block of mass m is placed on a rough wedge inclined at an angle α to the horizontal, a distance d up the slope from the bottom of the wedge. The coefficient of kinetic friction between the block and wedge is given by µ_0x/d, where x is the distance down the slope from the...
A couple of forces act on the screw and create the turning effect. But after sometime it gets harder. So, net torque is decreasing, but why is it decreasing? Frictional force comes into action, but friction doesn't depend on surface area. So, frictional force will remain constant.
So what...
Homework Statement
Example 2.12 : A block pulled on a horizontal table with friction. A block of weight 100 Newtons rests on a horizontal table. The coefficient of static friction between the block and the table is µs = 0.8.
a. If someone pulls on the block with a force F in the direction 37◦...
Hi
So I am busy studying rotational motion and there's an example in the book where they explain that when a car brakes the force of friction acts as a torque force which explains why a car lifts up at the back when braking.
Because the car does no rotational motion they say the net torque is...
Homework Statement
A ladder of length 5 m is resting against a SMOOTH wall, its point of contact being just below a first floor window. The bottom of the ladder rests on the ground and the coefficient of friction between the ladder and the ground is 0.28
A person of mass 78 kg climbs the...
<< Mentor Note -- Two threads on the same subject have been merged >>
I am a junior enrolled in IB Physics at the standard level at my high school. As a part of the curriculum we must perform an Internal Assessment (IA) which involves performing an experiment and performing calculations and it...
Homework Statement
A 1500 kg car is traveling at a speed of 30.0 m s-1 when the driver slams on the brakes and skids to a halt. Determine the stopping distance if the car is traveling down a 10o slope. The coefficient of kinetic friction between the car
and the road is 0.80.
Homework Equations...
Homework Statement
Determine the coefficient of friction for a surface when the mass of an object is 300g and the angle of incline when the object starts to move is 29°
Distance traveled and acceleration are not provided
Homework Equations
W = mg
Ffric = μN
N = mg cos(θ)
μN = mg sin(θ)
The...
Homework Statement
A student pushes a 0.65kg box Ali g a desk. When he stops pushing the book, it moves 85cm before stoping (slowing down in this period). Coefficient of friction between book and Table is 0.27.Calculate the work done on the book by the friction. Should it be positive or...
1. A crate resting on a rough horizontal floor is to be moved horizontally. The coefficient of static friction is 0.40. To start the crate moving with the least possible applied force, in what direction should the force be applied?
a. Horizontal
b. 24 degrees below horizontal
c. 22 degrees...
Homework Statement
Homework Equations
W = Fk d cos θ
Fk = FN μκ
The Attempt at a Solution
Here's my work :
m = 1 kg vi = 10 m/s vf = 0 m/s xi = 0 m xf = 0.1 m d = 0.1 m k=60 N/m μκ=?
The work done be the frictional force :
W = Fκ d cos θ = FN*μκ*d*cosθ = mg μκ d cos 180 =...
Homework Statement
Homework Equations
W = ΔUg + ΔkE + ΔUs
KE = 0.5 m v^2
Ug = m g h
Us = 0.5 k x^2
The Attempt at a Solution
k = 60 N/m vi=0 m/s (" the block is released from rest ") xi= 0 m/s ( "the spring is unstreached") vf= 0 m/s xf= 0.2 * sin 37 = 0.2*0.6 = 0.12 m d= 0.2 m...
I'm new to the forum and after some help if anyone can explain. I've read a few articles now, which have stated that the average co-efficient of friction for a tire with tread will be between 0.4 in the wet and 0.7 in the dry. If instead the tire had no tread, the co-efficient of friction will...
Im a high school student and am in AP Physics 1. I just created a formula for calculating the coefficient of kinetic/static friction between two objects using only distance and time (I don't have a way to measure Newtons). Is it correct and can it be used in the real world?
Hi Friends,
So I'll go into a bit of the setup that I'm having some trouble figuring out. I have a piece of rubber that will be pushing up against the side of a metal (or plastic) container to create a waterproof seal. The easiest way to think about this would be to imagine the rubber piece of...
Homework Statement
The coefficient of friction between A and the table is μA.
The coefficient of friction between A and B is μB.
A, B, C and D all move with an acceleration of 2m/s^2 (A and B move to the left).
Find the force that the friction between the bodies apply on B.
Find the tension of...
Homework Statement
Homework Equations
F = ma
Fr = uK * N
The Attempt at a Solution
My answer is 7 but it is not one of the choices
Thanks in advance[/B]
Hi everyone,
Me and a friend discussed a problem relating to a rotating reference frame, and somehow got to this question which we can't fully figure out, or maybe we are missing something. so, here goes:
On Earth's equator, our tangential velocity is ~1700 km/hr. A satellite orbiting right...
Homework Statement
Another question with the same idea, These questions bother me a lot. Hopefully you can help me figure why they solve it this way.
https://image.prntscr.com/image/aRnAD33ES2mML5JBwQBQvQ.png
it said in the question that U = 0.6 without saying if it is static or kinetic...
Homework Statement
You are presented with a circumstance in which three children are playing on a frozen pond. The three small children of mass 20.00 kg, 24.00 kg, and 16.00 kg, respectively, hold hands, and are pulled across a smooth frozen pond by a larger boy on skates, who pulls a...
Homework Statement
For a project we have to find a movie scene and calculate using any variables we can find. I am using Back to the Future and want to calculate the distance the DeLorean travels in one of the first scenes when they're first using it. I'd also like to find the acceleration from...
Homework Statement
If the car is going 30 m/s half way up the loop and loses energy due to friction at a rate of 2.0J per meter of track, how fast will it be going at the top?
(this is question related to the loop of roller coaster track, with radius 20m.)
Homework Equations
1. Ki + Ui = Kf +...